In recent years, a broadband has been requested with respect to a broadband wireless communication system. There exists WiMAX (Worldwide Interoperability for Microwave Access) to which, for example, an orthogonal frequency division multiplexing (OFDM)/orthogonal frequency division multiple access (OFDMA) method is applied in the broadband wireless communication system. WiMAX is also called IEEE (Institute of Electrical and Electronic Engineers) 802.16e.
The OFDM/OFDMA method is a method to communicate by multiplexing a plurality of different frequencies. Hereinafter, WiMAX will be explained as one example of the broadband wireless communication system to which the OFDM/OFDMA method is applied.
FIG. 2 is a view depicting one example of a frame structure of OFDMA WiMAX. A horizontal axis thereof indicates OFDMA symbols (time), and a vertical axis thereof indicates subchannels logical numbers (frequencies). A frame is structured by a set of a downlink sub frame (DL sub Frame) and an uplink sub frame (UL sub Frame). The downlink sub frame is a sub frame for reception, and the uplink sub frame is a sub frame for transmission.
The downlink sub frame is structured by a preamble (PREAMBLE), a frame control header (FCH), downlink maps (DL-MAP), an uplink map (UL-MAP), and a plurality of downlink bursts (DL Burst #1 to #7). The preamble represents a first mark of the frame. The frame control header includes control data. The downlink man represents data allocation information in the downlink sub frame. The uplink map represents data allocation information in the uplink sub frame. The downlink bursts represent user data.
The uplink sub frame is structured by a ranging channel (Ranging) such as initial ranging, periodic ranging, bandwidth request ranging, and handover ranging, an acknowledgement channel (ACK-CH) for HARQ, a fast feedback channel (CQICH), uplink bursts (UL Burst #1 to #3) from a plurality of terminals, and so on.
Herein, data types in the uplink sub frame are broadly divided into two types, the ranging channel, the acknowledgement channel, and the fast feedback channel are called the control data, and the uplink bursts are called the user data.
The control data is placed as the control data for transmission/reception of data for electric power control, timing control and transmission quality necessary for wireless communication, and the user data is placed as transmission/reception data such as audio data, image/moving image data with a user.
Herein, the fast feedback channel in the control data is a slot to be allocated periodically in order that control information such as channel quality indicator (CQI) notification and a request to switch an anchor wireless base station for handover (transferring a mobile station from one base station to another) is instructed immediately to a wireless base station. The single slot includes a plurality of OFDMA symbols.
Further, the channel quality indicator (CQI) notification represents a channel quality transmission method, and a base station device performs frequency scheduling by allocating data that the base station device transmits to each mobile station to a subcarrier whose reception quality is good, and thereby, the mobile station transmits each of the channel quality indicators (CQI) in each subcarrier with respect to all the subcarriers to the base station device. The base station device determines the subcarriers, a modulation method, and a coding rate used in each of the mobile stations considering the channel quality indicators (CQI) transmitted from each of the mobile stations in accordance with predetermined scheduling algorithm. A single subchannel includes the plurality of subcarriers (frequencies).
FIG. 3 is a view depicting a schedule of frame structure processing in a mobile station device. A time t1 represents a software operation start time. At the time t1, calculation operation processing of a CQI value (data) is performed by software processing.
A time t2 represents a closing time of the CQI data. After the time t2, rectangular data allocation processing, user data allocation processing, and rotation/renumbering processing is performed by hardware processing.
The mobile station structures the uplink sub frame with each of the control data including the channel quality indicators (CQI) and the user data, however, there exists a rule in a allocation method of the data in a frame structure. It is determined so that the control data secures an area rectangularly to allocate rectangular data thereto, and the user data is allocated thereto avoiding the control data. Therefore, in general, the control data such as the ranging channel, the acknowledgement channel, and the fast feedback channel is allocated on the uplink sub frame rectangularly, and then the user data is allocated on the uplink sub frame avoiding the area where the control data is allocated, and thereby the uplink sub frame is structured.
After that, when designation is given, the rotation/renumbering processing is performed. The rotation processing is a function to reallocate (randomize) the above-described logical allocation area in accordance with a rule. A method thereof is defined in IEEE 802.16-2004/802.16e (8. 4. 6. 2. 6). Concretely, data corresponding to the subchannel to be an object in each slot column in a time axis direction is rotated in a frequency direction, and thereby allocation is changed. The renumbering processing is processing to reallocate the data to the subchannel indicated by an effective bitmap depending on physical bit map information with respect to the result after the rotation processing to convert to physical mapping.
After the above-described processing is completed, at a time t4, the data is transmitted in synchronization with a transmission timing of the uplink sub frame. The time t4 represents a closing time of the frame structure.
However, there arise problems as will be described below in the frame structure processing. Normally, a calculation of the CQI value is performed including the software processing, and a large number of operation processing is necessary, resulting that it is common that a long period of time may be needed. Further, the mobile station device that receives an instruction from the wireless base station has to transmit the fast feedback channel to the uplink sub frame of the subsequent frame, therefore, time for the calculation of the CQI value is limited.
Also, as for the structure of the uplink sub frame, there exists the rule in the allocation method as described above, accordingly, the CQI data has to be set prior to the user data. Further, in the case when the subsequent processing of rotation/renumbering is needed after the data is allocated, the time t2, which is the closing time of the CQI value, is needed to be set in consideration of the above processing time.
Consequently, time for calculating the CQI value becomes short and the software processing is oppressed to be in time for the closing time t2.
FIG. 4 is a view depicting an example of the schedule of the frame structure processing in the case when CQI value calculation processing is in time for the time t2, and corresponds to FIG. 3. It is set as follows, an operation amount becomes large in the CQI value calculation processing, and thus a period of time T1, which is from the time t1 to a time t3, is taken, and the time t3, which is the time when the CQI value calculation processing ends, passes the time t2, which is the closing time of the CQI data. In this case, the CQI data cannot be transmitted at the time t4, which is the closing time of the frame structure, resulting that communication abnormality is caused.
Japanese Laid-open Patent Publication No. 2006-325264 discloses a base station device, which is a base station device performing wireless communication by using a multicarrier communication band divided into a plurality of blocks, and includes: an allocation unit allocating one of the plurality of blocks to first transmission data based on communication quality of each of the blocks, whereas allocating one of the plurality of blocks to second transmission data different from the first transmission data not being based on the communication quality of each of the blocks but in accordance with a predetermined pattern; and a hopping unit performing frequency hopping for the first transmission data and the second transmission data allocated to each of the blocks in each of the blocks.
Further, International Publication Pamphlet No. WO2005/020488 discloses a wireless communication device including: a subcarrier allocation unit allocating first data meeting a predetermined condition to a subcarrier selected by scheduling based on reception quality information indicating reception quality of each communication partner and request transmission rate information indicating a request transmission rate of each communication partner, whereas allocating second data different from the first data to a predetermined subcarrier; and a transmission unit transmitting the first data and the second data allocated to the subcarrier by the subcarrier allocation unit.
Further, Translated National Publication of Patent Application No. 2007-526692 discloses a CQI transmission method, which is a method in which a receiver station transmits a channel quality indicator to a transmitter station in a wireless communication system including a diversity mode consisted of spaced apart subcarriers and a band adaptive modulation and coding (AMC) mode consisted of a number of bands including a predetermined number of adjacent subcarriers, and includes the steps of: transmitting an average carrier to interference and noise ratio (CINR) value for a full frequency in the case when the receiver station operates in the diversity mode; and transmitting a different CINR of a predetermined number of bins in the case when the receiver station operates in the band AMC mode.